Crater should do runs against builds with llvm assertions in (by default)

[aidanhs]

This used to be the case, but changed. This will mean splitting up the set of builds perf and crater use.

See

• Disable LLVM assertions on Nightly, enable them in "alt" builds. rust#45810 (comment)
• Deploy builds both with asserts enabled and asserts disabled to CI. rust#46354

[Mark-Simulacrum]

We now also don't publish builds to the try bucket - everything goes into the two standard ci buckets, alt and non-alt, for all builds.

[aidanhs]

Yeah I have a patch on the try box I'm going to push up.